1. Field of the Invention
This invention relates to a structure of plasma display panels.
The present application claims priority from Japanese Application No. 2007-156285, the disclosure of which is incorporated herein by reference.
2. Description of the Related Art
In the typical arrangement of plasma display panels (hereinafter referred to as “PDPs”), two opposing substrates are placed on either side of a discharge space, between which row electrode pairs and column electrodes are disposed and respectively extend in the row direction and the column direction at right angles to each other, so that discharge cells arranged in matrix form on the panel surface are formed in areas within the discharge space corresponding to the intersections of the row electrode pairs and the column electrodes. The PDP initiates discharges between one of each row electrode pair and the column electrode and between the row electrodes constituting each row electrode pair in the discharge cells. These discharges result in the emission of visible light from phosphor layers in the three primary colors, red, green, blue, provided in the respective discharge cells to generate a matrix-display image.
Some PDPs having such a structure conventionally comprise column electrodes extending in the column direction and each composed of a portion facing the upper portion of the panel surface and a portion facing the lower portion.
A conventional PDP having such a structure is disclosed in Japanese Patent Laid-Open No. H11-65486.
A PDP comprising such column electrodes each composed of upper and lower divisions produces the advantage of improvement in screen brightness. This is because, in the address discharge period (writing discharge period) when the PDP is driven, data pulses are applied individually to the upper division and the lower division of each column electrode to initiate the address discharge. This enables the shortening of the address discharge period to approximately half of that of earlier PDPs, which in turn enables the setting of an increased period of the sustaining discharge which is produced for the emission of visible light.
However, such PDPs comprising column electrodes each composed of upper and lower divisions have the following problem in the manufacturing process.
Specifically, in a typical PDP manufacturing process, a sandblasting technique is often used in the step of shaping partition walls on the substrate for partitioning the discharge space into discharge cells.
When the sandblasting technique is used for shaping partition walls of a PDP which comprises column electrodes each composed of an upper and a lower division as described above, in the step of using the sandblasting technique to shape the partition-wall layer, the amount of electrostatic charge varies between one portion of the partition wall layer corresponding to the boundary portion between the upper and lower divisions of each column electrode (the portion of the partition wall layer not facing the column electrode) and the remaining portions of the partition wall layer (the portions of the partition wall layer facing the column electrode). As a result, the sandblasting causes surface unevenness on the partition wall layer.
For this reason, in the subsequent calcination process, the surface unevenness caused by the sandblasting effects variations in the degree of shrinkage of the partition wall layer accompanying the calcinations between the portion of the partition wall layer facing the boundary portion of the column electrode and the remaining portions. As a result, the shape of the partition wall thus produced is out of the required shape, which then gives rise to the impossibility to form uniform discharge cells over the panel surface.
When the discharge cells cannot be uniformly formed over the panel surface as a consequence of this, the image displayed on the screen is uneven (hereinafter referred to as “uneven display”).
Also, when such a sandblasting technique is used in the step of shaping the partition wall, for similar reasons, the partition wall has a greater height in the portion facing the boundary portion of the column electrode than in the remaining portions. As a result, the partition wall is in uneven contact with the structural components on the substrate facing the partition wall in this area, which may cause an audible noise.
On the other hand, when the sandblasting technique is not used for forming the partition wall, in the area corresponding to the boundary portion of each column electrode, a misalignment produced when the two substrates are placed on one another to face each other effects a change in the opposing area between the row electrode pair provided on one substrate and the column electrode provided on the other substrate. As a result, here again, an uneven display may occur on the screen.
This problem of an uneven display occurring on a PDP comprising column electrodes each composed of two divisions becomes much more notable in the development of a PDP capable of generating a high definition image such as the recently developed full HD display, because the shape of each discharge cell is smaller than that in a conventional PDP.